/Engine/Source/Editor/UnrealEd/Public/Layers/LayersSubsystem.h
Selects/de-selects actors belonging to the named layer.
true if at least one actor was selected/deselected.
virtual bool SelectActorsInLayer ( const [FName](API\Runtime\Core\UObject\FName) & LayerName, const bool bSelect, const bool bNotify, const bool bSelectEvenIfHidden, const [TSharedPtr](API\Runtime\Core\Templates\TSharedPtr)< [ActorFilter](API\Editor\UnrealEd\Layers\ULayersSubsystem\ActorFilter) > & Filter )